Mechanism of Visible-Light Photocatalytic Mineralization of Indigo Carmine Using ZnBi2O4-Bi2S3 Composites

Novel highly visible-light active ZnBi2O4-Bi2S3 photocatalysts with various weight percentages of Bi2S3 have been synthesized by a simple two-step co-precipitation and hydrothermal method. The efficacy of the as-prepared ZnBi2O4-Bi2S3 composites was evaluated for the degradation of Indigo carmine in aqueous solutions under visible light irradiation. It was found that the as-prepared ZnBi2O4-Bi2S3 composites showed was greatly enhanced photocatalytic activities as compared to that of pristine ZnBi2O4 under visible light, which could be attributed to synergetic effects, charge transfer between ZnBi2O4 and Bi2S3, as well as the separation efficiency of the photogenerated electrons and holes. The superoxide anion radical was the major active species responsible for the photodegradation process, whereas the contributions of the photoinduced h(+) and hydroxyl radicals were moderate and minor, respectively. These results demonstrate the feasibility of utilizing ZnBi2O4-Bi2S3 as potential heterogeneous photocatalysts for environmental remediation.